Reverse thrust operations of a model scale Contra-Rotating Open Rotor design were
numerically modelled to produce individual rotor thrust and torque results comparable
to experimental measurements. The aims of this research were to develop an
understanding of the performance and aerodynamics of open rotors during thrust
reversal operations and to establish whether numerical modelling with a CFD code can
be used as a prediction tool given the highly complex flowfield.
A methodology was developed from single rotor simulations initially before building a
3D‘frozen rotor’ steady-state approach to model contra-rotating blade rows in reverse
thrust settings. Two different blade pitch combinations were investigated (β1,2 =+30°,-
10° and β1,2 =-10°,-20°). Thrust and torque results compared well to the experimental
data and the effects of varying operating parameters, such as rpm and Mach number,
were reproduced and in good agreement with the observed experimental behaviour. The
main flow feature seen in all the reverse thrust cases modelled, both single rotor and
CROR, is a large area of recirculation immediately downstream of the negative pitch
rotor(s).This is a result of a large relative pressure drop region generated by the suction
surfaces of the negative pitch blades.
An initial 3D unsteady sliding-mesh calculation was performed for one CROR reverse
thrust case. The thrust and torque values were in poor agreement with experimental
values and the disadvantages relating to time costs and required computational
resources for this technique were illustrated. However, the results did yield a nominal
unsteady variation of thrust and torque due to rotor phase position.
Overall the work shows that it may be possible to develop a CROR reverse thrust
prediction tool of beneficial quality using CFD models. The research also shows that the
frozen rotor approach can be adopted without undermining the fidelity of the results.
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/10448 |
| Date | 06 1900 |
| Creators | McCarthy, Martin |
| Contributors | MacManus, David G. |
| Publisher | Cranfield University |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Doctoral, MSc by Research |
| Rights | © Cranfield University, 2011. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. |
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